Pentostatin (2'-Deoxycoformycin) is a tight-binding inhibitor of __enosine Deaminase which has been used as a therapeutic agent for a number of disorders including hairy cell leukemia. Our hypothesis is that Pentostatin will be an effective agent for the treatment of refractory rheumatoid arthritis of doses that have little or no toxicity through inhibition of the proliferation of T-lymphocytes.